The present invention relates to a numerical control system (referred to as NC hereinbelow) used in combination with a numerically-controlled machine tool (referred to as NC machine hereinbelow) so as to function very effectively when a work piece to be worked has many different kinds of repeatable work processes.
Many of the pieces worked by the NC machine involved several kinds of repeatable worked shapes. In order to work many pieces in the same shape patterns, a command tape must be prepared for each of the patterns. This leads to the following disadvantages.
(1) It takes a long time to prepare a command tape. PA1 (2) The number of errors in the command tape prepared tends to be increase. PA1 (1) The sub tape reader needs additional space. PA1 (2) The command tape for a repeatable work process, which is repeatedly used, can be easily damaged or smudged.
Heretofore, there have been proposed methods to compensate for such disadvantages. According to the first prior art, an electronic circuit is used to set up several specified kinds of working patterns which are frequently and commonly adopted, thereby permitting simple preparation of command tapes in cases where such specified kinds of working patterns are used to work a piece. This is called "fixed cycle".
With the second prior art an additional tape reader (referred to as sub tape reader hereinbelow) is provided. A command tape for a repeatable pattern is set in said sub tape reader. When the repeatable pattern is requested with the command tape set on the primary tape reader (referred to as main tape reader hereinbelow), a piece is cut in the requested patterns by changing a sub tape reader which operates with the particular command.
However, there occurs very frequently the necessity of working the patterns originally specified by the respective users. The first prior art is not applicable to such unique working patterns which are different from the predetermined specified fixed pattern, required by the users. Further, in case of the second prior art, the following drawbacks can not be avoided.